1. Field of the Invention
The invention relates to a hybrid vehicle. More particularly, the invention relates to a hybrid vehicle provided with an internal combustion engine that has an exhaust gas control apparatus with an exhaust gas control catalyst that purifies exhaust gas provided in an exhaust system, and that is capable of outputting power for running, an electric motor capable of inputting and outputting power for running, and a secondary battery capable of sending and receiving electric power to and from the electric motor.
2. Description of the Related Art
Japanese Patent Application Publication No. 2009-262677 (JP-A-2009-262677), for example, describes one such hybrid vehicle that is provided with an engine in which a catalyst that purifies exhaust gas is provided in an exhaust passage, a first motor-generator, a power split device that is connected to the engine, the first motor-generator, and a drive shaft, a second motor-generator that is connected to the drive shaft, and a battery that sends and receives electric power to and from the first motor-generator and the second motor-generator. When a temperature of the catalyst is higher than a temperature threshold value (such as a temperature at which the degree of catalyst degradation increases, i.e., a temperature at which the catalyst deteriorates) when the vehicle is decelerating, the hybrid vehicle controls a fuel supply valve of the engine such that a fuel cut is not performed, and controls a throttle valve of the engine such that engine torque shifts more from positive torque to negative torque with a higher state-of-charge (SOC) of the battery and as an amount of air that is supplied to the engine becomes greater than an air amount threshold value (such as an air amount that will cause the engine to misfire). With this hybrid vehicle, deterioration of the catalyst and overcharging of the battery are suppressed by controlling the fuel supply valve of the engine so that a fuel cut is not performed, and controlling the throttle valve of the engine such the amount of air supplied to the engine becomes larger than an air amount threshold value and the engine torque becomes negative torque, when the temperature of the catalyst is higher than the temperature threshold value and the SOC of the battery is higher than a SOC threshold value.
With the hybrid vehicle described above, when the temperature of the catalyst is higher than the temperature threshold value when the vehicle is decelerating, the promotion of catalyst degradation is suppressed by controlling the fuel supply valve so that a fuel cut will not be performed and the like. However, in order to further suppress the promotion of catalyst degradation, it is preferable to have more opportunities to perform this control.